Event Storming and Event Modeling from the trenches

In 2014 I had the chance to join a workshop on Event Storming by Alberto Brandolini at BuildStuff. After that I started to practice it intensively at work and was quickly convinced that it was a very interesting asset to do my job. Indeed, as a consultant I meet many teams, and need to understand in a few hours as much context as possible. It is surprising how, with the right tool, you can even learn things about the job that business experts themselves were missing because they lack time to think about it. 
In 2019, I added another string to my bow thanks to a workshop on Event Modeling by Adam Dymitruk and Greg Young in Lyon. As already explained, it covers some lacking for me in the Event Storming approach, and thus I find it to be a very complementary method to Event Storming. The synergy of both tools can be huge.
I would like to share with you how they help me to improve my craft, plus give you some tricks from the trenches. 

Event Storming from the trenches 

A quick lesson I learned from early Event Storming is that all Event Storming are different, and this is great. Of course, they are different in terms of content, but what I mean is that they can also be really different in form. Because they will always adapt to your context!
For instance, it is sometimes enough to put only the events (no commands, aggregates or even contexts), because it will trigger the necessary discussion, and you won’t need to go further.   

An important point is to agree before the Event Storming on why you are doing it. You want to cover a new feature? You want to explain the business to someone else? You want to clarify a point with your team? Depending on the end goal, the form should be adapted to suit your needs. 

By experience, the law of two feet works very well for an Event Storming workshop. You don’t want people to be disengaged, and you don’t need to have all the team all the time. Some might take a break while others are digging a specific point, and this is great. Collective intelligence at work! 

In terms of timing, I believe that half a day is basically the most that you can do if people are really invested. It can be exhausting to carry such a workshop for too long. Keep an eye on how people feel and don’t hesitate to call for a break if you feel like the mob need it. 
 
Something I rarely see when people talk about the Event Storming session they performed is drawing a link between events and commands between contexts, when an event in a context triggers a command in another one. It gives you an instant view of Bounded Contexts relationship, hence some hints to know if your contexts are well defined. 

Finally, after many attempts, I must say that for me, Event Storming is a killer tool to have a big picture view of a situation. I’ve seen it a bit less valuable when I needed to dig in the implementation on a specific part (in the solution space if you prefer). This is where Event Modeling came to the rescue! 

Event Modeling from the trenches 

One of the main feedback I had from my many Event Storming workshops is that losing the temporal link between the events was a shame, because it has a great value to describe business workflow. For me this is one of the main benefits of Event Modeling. 
It makes it very good to explore concrete implementation, to represent business workflow and to link it with the UI.  
 
And like Event Storming, it gives a very good domain view, especially when combine with Event Sourcing and CQRS. It is powerful to describe the solution workflow, as you imagine and then implement it. 
With time, as the model evolve and grows in maturity, it’s something really valuable to support technical and/or business discussion. 
As Adam would say, this is sort of a blueprint of the system that a business or a technical profile can understand easily. 

I find useful to take screenshots of such models to add into User Story as documentation, or even in Pull Request in order to describe which part of the system we updated (showing a picture before the Pull Request and after the Pull Request for instance).  

Another trick to reach an interesting model is to describe each workflow separately, even if we feel that some of them will be handled by the same piece of code. Then when all scenarios are well described as a unit, you can try to merge them into a single one that could theoretically handle all of them. But even there it’s interesting to keep a trace of all the single scenario that leads you to this design. 

Hope it helps! 

I hope these few tricks will help you to perform better Event Storming and Modeling sessions. I could add that whatever the workshop you do, capturing the end result in a Miro board (or equivalent tool) is usually a good idea for asynchronous communication and future evolution of the model.
But if you should keep only one thing from this article, it would be don’t worry too much about the form, keep whatever works well as an event driven description for your team, and don’t mind how you call it.  
 
Because domain events are the powerful idea here, Event Storming or Modeling are “just” a way to exploit it 🙂 

 

Ouarzy

 

Leave a Reply

Your email address will not be published. Required fields are marked *